Bill Hewlett and Dave Packard wanted to launch a technology company long before they had a specific product in mind. In 1937, Bill made a breakthrough while working as a researcher at Stanford. He worked on variable oscillators, instruments which generate pure tones and frequencies for use in producing and calibrating audio equipment. Bill wanted to solve the challenge of variable resistance — raising or lowering an oscillator’s signal to hit the desired levels was straightforward, but to avoid distortion, the resistance in the oscillator needed to increase or decrease in sync with the signal to maintain balance. No one had figured out an easy, inexpensive way to do that yet.

On July 27, 1938, Bill found his solution in a 15-watt lightbulb. By soldering the lightbulb and socket into an oscillator circuit, he created a resistor that would burn off excess power in the form of light and heat and thus provide dynamic resistance. The breakthrough led Hewlett-Packard to its first product.

After Bill and Dave began operations in the Addison Avenue garage in September 1938, they spent much of their time refining Bill’s design into a finished product. By November, they had a workable prototype, and by Christmas they had a production model, dubbed the 200A.

The 200A was a fast hit. One early fan was John “Bud” Hawkins, the chief sound engineer at Walt Disney Studios, who was developing the first commercial use of surround sound for Disney’s upcoming film Fantasia. Hawkins saw Bill’s prototype oscillator in November 1938 and eventually commissioned several custom models. Those models, whose modifications altered Bill’s design to hit a different frequency range, soon became available as the 200B.

The success of the 200A and 200B established HP’s future. On January 1, 1939 — not long after the 200A production model was finished — Bill and Dave formalized their partnership by establishing Hewlett-Packard Company.